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Water Rise in Cappilary Tube - Where does the energy come from?

  1. Mar 5, 2012 #1
    If a small tube (capillary tube) is dipped into the water, the water level rises. Which means someone is doing work on the water to rise it against gravity. My question is, who is doing this work?
    My guess is the internal energy of the molecules is doing the work. That also means that temperature decreases slightly when rising the water. Is this the case?
     
  2. jcsd
  3. Mar 5, 2012 #2

    Sum

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    This is what i think:
    Adhesion forces btn water molecules and the walls of the tube do the work of moving water up.
     
  4. Mar 5, 2012 #3
    My guess:
    If adhesion forces are kind of electrostatic forces, then the work is done by the electrostatic energy.
     
  5. Mar 5, 2012 #4
    Yes, its the adhesion force (hydrogen bonding for water). In terms of energy, there is potential energy stored in the broken chemical bond. When the water and tube form a hydrogen bond, the chemical potential energy is released and becomes gravitational potential energy, i.e. the column of water rises. Forming chemical bonds releases potential energy (think explosives), and breaking bonds requires energy. To get a drop of water off a piece of glass, you have put energy in, such as by heating it or pulling it with a dropper.
     
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